pure javascript to check if something has hover (without setting on mouseover/out)

Simply using element.matches(':hover') seems to work well for me, you can use a comprehensive polyfill for older browsers too: https://developer.mozilla.org/en-US/docs/Web/API/Element/matches

You can use querySelector for IE>=8:

const isHover = e => e.parentElement.querySelector(':hover') === e;    

const myDiv = document.getElementById('mydiv');
document.addEventListener('mousemove', function checkHover() {
  const hovered = isHover(myDiv);
  if (hovered !== checkHover.hovered) {
    console.log(hovered ? 'hovered' : 'not hovered');
    checkHover.hovered = hovered;
  }
});

.whyToCheckMe {position: absolute;left: 100px;top: 50px;}

<div id="mydiv">HoverMe
  <div class="whyToCheckMe">Do I need to be checked too?</div>
</div>

to fallback I think it is ok @Kolink answer.

First you need to keep track of which elements are being hovered on. Here's one way of doing it:

(function() {
    var matchfunc = null, prefixes = ["","ms","moz","webkit","o"], i, m;
    for(i=0; i<prefixes.length; i++) {
        m = prefixes[i]+(prefixes[i] ? "Matches" : "matches");
        if( document.documentElement[m]) {matchfunc = m; break;}
        m += "Selector";
        if( document.documentElement[m]) {matchfunc = m; break;}
    }
    if( matchfunc) window.isHover = function(elem) {return elem[matchfunc](":hover");};
    else {
        window.onmouseover = function(e) {
            e = e || window.event;
            var t = e.srcElement || e.target;
            while(t) {
                t.hovering = true;
                t = t.parentNode;
            }
        };
        window.onmouseout = function(e) {
            e = e || window.event;
            var t = e.srcElement || e.target;
            while(t) {
                t.hovering = false;
                t = t.parentNode;
            }
        };
        window.isHover = function(elem) {return elem.hovering;};
   }
})();

it occurred to me that one way to check if an element is being hovered over is to set an unused property in css :hover and then check if that property exists in javascript. its not a proper solution to the problem since it is not making use of a dom-native hover property, but it is the closest and most minimal solution i can think of.

<html>
    <head>
        <style type="text/css">
#hover_el
{   
    border: 0px solid blue;
    height: 100px;
    width: 100px;
    background-color: blue;
}   
#hover_el:hover
{   
    border: 0px dashed blue;
}
        </style>
        <script type='text/javascript'>
window.onload = function() {check_for_hover()};
function check_for_hover() {
    var hover_element = document.getElementById('hover_el');
    var hover_status = (getStyle(hover_element, 'border-style') === 'dashed') ? true : false;
    document.getElementById('display').innerHTML = 'you are' + (hover_status ? '' : ' not') + ' hovering';
    setTimeout(check_for_hover, 1000);
};
function getStyle(oElm, strCssRule) {
    var strValue = "";
    if(document.defaultView && document.defaultView.getComputedStyle) {
        strValue = document.defaultView.getComputedStyle(oElm, "").getPropertyValue(strCssRule);
    }
    else if(oElm.currentStyle) {
        strCssRule = strCssRule.replace(/\-(\w)/g, function (strMatch, p1) {
            return p1.toUpperCase();
        });
        strValue = oElm.currentStyle[strCssRule];
    }
    return strValue;
};
        </script>
    </head>
    <body>
        <div id='hover_el'>hover here</div>
        <div id='display'></div>
    </body>
</html>

(function getStyle thanks to JavaScript get Styles)

if anyone can think of a better css property to use as a flag than solid/dashed please let me know. preferably the property would be one which is rarely used and cannot be inherited.

pure javascript to check if something has hover (without setting on mouseover/out)

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